Good 8" drivers for Tapped horns with long path lengths? - Page 4 - diyAudio
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Old 16th February 2014, 06:10 PM   #31
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Quote:
Originally Posted by JLH View Post
I tried your suggestion. It virtually made no difference. I can barely see the difference when I do the "compare previous" command. Historically, my Horn Response predictions have measured very close using Conical sections for the simulation. Is there a significant reason for your suggestion? Did I miss a conversation somewhere?
As long as none of the segments are extremely long it won't make a significant difference in your graphs (depending on how you define "significant", I guess). It will, however, make quite a big difference in the net volume reported on the Schematic screen.

I noticed that the specs you used are not even close to the published specs, are they measured specs? If so, what was the Le? 1.8 less than shown?

EDIT - a quick search for your name and keyword w8-740 shows these are measured specs, and Le is 2.8 before adding 1.8 mh of extra inductance, as I thought. I just wanted to make sure I was following what you were doing.

Last edited by just a guy; 16th February 2014 at 06:19 PM.
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Old 16th February 2014, 07:02 PM   #32
JLH is offline JLH  United States
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Originally Posted by just a guy View Post
As long as none of the segments are extremely long it won't make a significant difference in your graphs (depending on how you define "significant", I guess). It will, however, make quite a big difference in the net volume reported on the Schematic screen.

I noticed that the specs you used are not even close to the published specs, are they measured specs? If so, what was the Le? 1.8 less than shown?

EDIT - a quick search for your name and keyword w8-740 shows these are measured specs, and Le is 2.8 before adding 1.8 mh of extra inductance, as I thought. I just wanted to make sure I was following what you were doing.
You got it correct.

Edit - Changing to Par only added 0.83 liters to the horn volume. That's not significant in my book.
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Last edited by JLH; 16th February 2014 at 07:14 PM. Reason: added comment
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Old 16th February 2014, 07:09 PM   #33
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Originally Posted by sine143 View Post
They are withing about 1 db of each other if both are graphed in 1 pi, and are the same size (140 liters pre fold).
The pre fold volume on my horn is 115 liters, not 140 liters.
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Old 16th February 2014, 08:24 PM   #34
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Originally Posted by JLH View Post
Changing to Par only added 0.83 liters to the horn volume. That's not significant in my book.
No, it's not. Usually there's quite a bit more discrepancy when switching from CON to PAR but I guess not in this case. I just use PAR when possible to avoid the issue. I have noticed that the larger the segments are the more difference there will be between CON and PAR, especially if the segments are long, and that's as far as I have studied this issue. For example, if the segment is ridiculously large you can see a difference of 1/3 volume. http://www.avsforum.com/t/1489784/ho...#post_23714999 - no need to read that, just look at the pictures. And I've noticed a fair bit of discrepancy with regular sized segments too, if the segment is very long like the middle segment in most constant expansion rate tapped horns. And the issue isn't volume alone, but a discrepancy in how the volume is distributed within the segment, since CON and PAR are very different shapes and this can lead to differences in the sim. But as long as the segments are very short this isn't a huge issue, I just like to be as accurate as possible.

Last edited by just a guy; 16th February 2014 at 08:43 PM.
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Old 16th February 2014, 10:25 PM   #35
sine143 is offline sine143  United States
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oh very nice. sorry I posted from phone, didnt have hornresp lol.
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Old 16th February 2014, 11:23 PM   #36
JLH is offline JLH  United States
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Quote:
Originally Posted by just a guy View Post
No, it's not. Usually there's quite a bit more discrepancy when switching from CON to PAR but I guess not in this case. I just use PAR when possible to avoid the issue. I have noticed that the larger the segments are the more difference there will be between CON and PAR, especially if the segments are long, and that's as far as I have studied this issue. For example, if the segment is ridiculously large you can see a difference of 1/3 volume. Horn Folding - a brief study of the centerline vs advanced centerline method - no need to read that, just look at the pictures. And I've noticed a fair bit of discrepancy with regular sized segments too, if the segment is very long like the middle segment in most constant expansion rate tapped horns. And the issue isn't volume alone, but a discrepancy in how the volume is distributed within the segment, since CON and PAR are very different shapes and this can lead to differences in the sim. But as long as the segments are very short this isn't a huge issue, I just like to be as accurate as possible.
Thank you for the detailed followup.
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Old 19th February 2014, 05:05 PM   #37
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Originally Posted by sine143 View Post
GM, your design is the MCM 8 correct? doesnt it only have 8mm of xmax?
Correct.

The data sht. I have lists a 16 mm Xmax, but Hc, Hg specs calculates only 8 mm, so all my 55-2421 Xmax sims are ~ 6 dB too optimistic.

GM
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Old 19th February 2014, 08:38 PM   #38
sine143 is offline sine143  United States
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Lol, well the jbl gto 804 and the infinity 860w are good substituions for the mcm, at around 40 a pop with 12-14mm xmax
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Old 19th February 2014, 09:08 PM   #39
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Hmm, these other two aren't good substitutions unless peak SPL over a narrow BW is the primary goal since they lack the MCM's fairly wide available gain BW [lower Qts].

GM
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Old 19th February 2014, 11:04 PM   #40
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the Gto 804 at least compares favorably to the mcm in Olivers 140 liter dual mcm8 design, yeilding about 4 db increased output with possibly .5 db more ripple.
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